Windscreen crack concerns on plane

Air New Zealand has denied passenger claims that one of its planes made a rapid descent after a crack developed in the cockpit's windscreen.

One passenger has told how the plane lost altitude quickly. The flight, from Auckland to Cairns on Sunday, was diverted to Brisbane where it landed safely.

"There was a moment when the aeroplane suddenly slowed down and we lost a lot of altitude," passenger Ruby Boussard told ABC Radio.

"The seat (belt) light came on. The air hostesses were very firm in telling us to go back to our place and put the rubbish away and clear the path."

But Air New Zealand said the plane made a gradual descent after the crack developed in the windscreen on the pilot's side of the cockpit.

"Contrary to reports in some media, the pilots followed a standard descent profile as an aircraft would preparing to land, gradually descending from approximately 34,000 feet to 23,000 feet over a period of seven minutes," it said in a statement.

The inside pane of the window, which is made up of three separate panes of glass, had cracked.

The statement said the crack did not risk the integrity of the windscreen.